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  1. AFex54

    SOT-23 Transistor ''750'' marking?

    Here are the photos. On one side they are beside a couple of AON7403 MOSFETS, a small amount of water got on this area and I want to replace the mosfets and 750 transistors here to see if it fixes the issue. There a 2 power inputs on this graphics card, the card powers up and gives ''no...
  2. AFex54

    SOT-23 Transistor ''750'' marking?

    I can get some photos later, It has a ''Q'' PCB marking, there are also other SOT23 packages near it with ''D'' PCB marking.
  3. AFex54

    SOT-23 Transistor ''750'' marking?

    I looked thoroughly and couldnt find what part this is. there was only a couple SOT23 part codes online that even contained ''750'' and they are diodes. There are a large number of them located in the power supply input area of a graphics card for a computer.
  4. AFex54

    How to make this circuit unity gain?

    I forgot to ask should the 22r emitter resistors be rated at high wattage like the original 5w 100r emitter?
  5. AFex54

    How to make this circuit unity gain?

    really helpful everyone, learning these smalls bits of electronic theory really adds up, knowing just a few pieces of the puzzle makes the whole thing a lot less obscure.
  6. AFex54

    How to make this circuit unity gain?

    This helped tremendously, the amp has more depth, weight and speed to its sound. would there be any way to build even further on this design, maybe adding additional transistors? this may seem excessive but its driving a particularly power hungry planar magnetic headphone, they require much...
  7. AFex54

    How to make this circuit unity gain?

    thanks for the help, looking forward to see how this affects the sound.
  8. AFex54

    How to make this circuit unity gain?

    this helps a lot. how necessary are those resistors? I already have the bd140 and diodes on hand but would need to place an order for the resistors
  9. AFex54

    How to make this circuit unity gain?

    thanks, it worked. I read that Non-inverting amps cant have a gain lower than 2 but this seems to contradict that. after removing R3 feedback resistor aswell it seems to sound better. how would you implement the extra transistors and diodes into the circuit?
  10. AFex54

    How to make this circuit unity gain?

    https://i.imgur.com/2g5Hoeg.png I built this amp but the gain is unncessary I just need it to be a buffer between the headphones and source to supply the power the headphones need. I think the way to achieve this is to remove the caps and resistors on the op amp's inverting inputs but will this...
  11. AFex54

    Volume control potentiometer is mute for first 10%?

    I built a simple volume control using a 47k log pot and it works great except for the first the 10% of where it is mute and then jumps up in volume, the remaining 90% is good and precise ... is this because the resistance too high? If the resistance is a too high and I were to add a resistor...
  12. AFex54

    4066 switches leaking in sample and hold circuit?

    ok, thanks for the help so far
  13. AFex54

    4066 switches leaking in sample and hold circuit?

    Im not sure what constitutes 'constant' but the '9V' on the schematic is coming directly from a 9V mains adapter. I changed R to 10k and C to 1μF but it didnt have any effect, and I have added 2 decoupling caps already, a 1μf and 0.1 μf EDIT: I tested my mains adapter with a voltameter and it...
  14. AFex54

    4066 switches leaking in sample and hold circuit?

    Oh actually its not so perfect, I can sample without any delay but the samples arent consistent, if press the key multiple times the voltage drifts a small random amount each time EDIT: I figured I may aswell make a recording of it with my synthesizer since its working now. here is the same...
  15. AFex54

    4066 switches leaking in sample and hold circuit?

    Thank you, now it works perfectly! the purpose of this is simply to maintain what ever voltage the potentiometer produces after the SPST switch is opened, the potentiometers votlage determines the musical note of a voltage controlled oscillator. the voltage needs to be maintained because...
  16. AFex54

    4066 switches leaking in sample and hold circuit?

    like so?
  17. AFex54

    4066 switches leaking in sample and hold circuit?

    yes, about 5 seconds. if I press any key in that time the voltage doesnt change and the 5 second 'timer' resets, if i wait till after the 5 seconds pressing a different key will successfully sample a new voltage. Here is the redrawn circuit, the SPST switch is the key and the potentiometer...
  18. AFex54

    4066 switches leaking in sample and hold circuit?

    ahh! so the transistor is only there to generate a negative pulse for a 555... I really should have noticed this sooner since Ive used this exact circuit before in my analogue step sequencer and also since none of differentiators schematics online featured a transistor... well, that solves that...
  19. AFex54

    4066 switches leaking in sample and hold circuit?

    I checked again and now im getting 5V on the collector... not sure what im doing wrong, checked for bad solders and there isnt any so i guess theres no explanation
  20. AFex54

    4066 switches leaking in sample and hold circuit?

    ok. the intial problem I was having with the differentiator circuit above was that the CMOS switch was being held closed even when the spst button was open, the differentiator has 6.5V at 'out' with its input floating, do you know why this is? edit: sorry I think I made the mistake of trusting...
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